Pic. 4.40. Coolant circuit diagram: 1 - radiator; 2 - expansion tank with a lid; 3 – silicone element; 4 – a tank of a liquid for a screen wiper (heated by coolant); 5 - interior heater radiator; 6 – coupled heating control valve; 7 – block of cylinders; 8 - coolant pump; 9 - thermostat; A - feed; B - exit
Cooling system (pic. 4.40) serves to maintain the normal operating temperature of the engine. It includes a radiator with a thermostat; pipes and channels in the block and cylinder head in which coolant circulates. The circulation pattern of the coolant depends on its temperature and is regulated by a thermostat.
When starting a cold engine, the coolant first circulates through a small circuit, which is limited by the engine and the heating system.
Coolant circulates in the engine. So the engine warms up faster. The radiator is connected only when the coolant reaches a certain temperature.
As soon as the coolant temperature begins to rise, the thermostat opens the radiator and closes the small circuit at the same time. At operating temperature, coolant circulates through the lower cold fluid hose from the left radiator reservoir to the water pump, which forces fluid into the engine block, oil cooler, and cylinder head. Most of the liquid then flows back through the open thermostat through the upper coolant hose to the right radiator reservoir, and the other part goes to the radiator of the car's heating system. The cooled liquid flowing from the bottom of the radiator after passing through the circuit is heated and hot enters the radiator from above. As the hot water passes down the radiator fins, it cools down. If the water temperature falls below the prescribed operating temperature while driving, the thermostat closes the radiator again until the coolant is sufficiently warm.